Ardisia recurvipetala Julius, Siti-Munirah & Utteridge, sp. nov. (§ Crispardisia)

Julius, Avelinah, Siti-Munirah, Mat Yunoh & Utteridge, Timothy M. A., 2023, Ardisia recurvipetala (Primulaceae - Myrsinoideae), a new species from northern Peninsular Malaysia, PhytoKeys 232, pp. 89-98 : 89

Ardisia recurvipetala Julius, Siti-Munirah & Utteridge, sp. nov. (§ Crispardisia)

Figs 1 , 2 , 3

Diagnosis.

Ardisia recurvipetala is the only Ardisia species with the following combination of characters: leaf margins with both vascularised glands and pustule-like structures, lamina raised between the venation giving a somewhat bullate appearance, inflorescences on the main shoot and specialised lateral branches, white flowers with recurved petals with a pink patch at the base of the corolla lobes.

Type.

Malaysia. Peninsular Malaysia: Terengganu, Hulu Terengganu Distr., Taman Negeri Kenyir , 5°01'00.5"N, 102°32'29.9"E, 201 m elev., 15 June 2022 (fl. & fr.), Siti Munirah FRI 98670 (holotype KEP!; isotype BORH!) .

Woody shrub ca. 1 m tall. Branches 5-12.5 cm long. Indumentum absent except for short, white or brown, simple eglandular and glandular hairs on reproductive parts. Leaves spirally arranged; petioles (0.5-) 1-1.5 cm long, winged by the decurrent leaf base, glabrous; lamina chartaceous, with sparse black gland dots throughout abaxially, raised between the venation; usually broadly elliptic, occasionally oblanceolate, (12.5-)17.5-20.5 × 4.5-7.5 cm (excluding reduced leaves subtending inflorescences on specialised lateral branches); young leaves light green, mature leaves dark green above, pale green beneath; base cuneate; margin crenate with vascularised glands (bacterial nodules) at the incision between crenatures and with pustule-like structures along the crenations from projecting venation; apex acute to obtuse; glabrous on both surfaces; mid-rib flat above, raised below; lateral veins 9-14 pairs, irregularly spaced, joining at the marginal vein, distinct on the adaxial surface, prominent on abaxial side; intersecondary veins sometimes present; intercostal veins obscure. Inflorescences subsessile, terminal on main shoot and on relatively short specialised lateral branches with 1-2(-3) subtending leaves, condensed racemose, ca. 2 × 3 cm, unbranched, 10-18-flowered. Flowers 5-merous; pedicels brownish-red, 1-1.5 cm long, slender, densely glandular hairy with globular tips, covered with dense, brown gland dots; sepals yellowish-green, pale pink at base, not overlapping, covered with dense brown gland dots, triangular-ovate, 1.5-2 × 1-1.5 mm, sparsely glandular hairy abaxially, glabrous adaxially, margin ciliate with laxly spaced, simple, pale brown hairs, apex obtuse; corolla tube ca. 0.5 mm long, lobes 5, white except the creamy-white apex and pinkish base, covered with dense, brown gland dots, lanceolate, 6-7 × 3-4 mm, glabrous on both surfaces, apex acute, strongly recurved at anthesis; stamens 5, yellowish, subsessile, anthers narrowly lanceolate-mucronate, 5-6 × 1.5 mm, glabrous throughout, gland dotted abaxially, thecae not locellate, dehiscent by longitudinal slits; ovary subglobose, ca. 2 × 1.5 mm, glabrous, ovules ca. 9 arranged in 1-series, style and stigma slender, ca. 5.3 mm long, glabrous. Young fruits globose, with dense gland dots, 4-6 × 4-6 mm, green, glabrous; pedicels becoming thickened and obconically flared, 1.8-2 cm long. Mature fruits not observed.

Distribution.

Endemic to Peninsular Malaysia, Terengganu (Taman Negeri Kenyir); currently known only from the type locality (Fig. 4 ).

Ecology.

Growing in a lowland dipterocarp forest at 201 m elev. in a shaded area not far from a small stream.

Etymology.

The species epithet is derived from its recurved corolla lobes.

Conservation status.

Data Deficient (DD). Ardisia recurvipetala is known from fewer than five individuals in flower and fruit collected from intact forest patches within the Taman Negeri Kenyir. The sites where the taxon was found were previously part of the Tembat Forest Reserve before it was gazetted into Taman Negeri Kenyir in 2018. Further surveys are needed to understand the threats at the type locality and if the species is distributed outside the current area and, until these data are obtained, the species is assessed as Data Deficient (DD) ( Chua and Saw 2006; IUCN Standards and Petitions Committee 2022).

Notes.

Peninsular Malaysian members of § Crispardisia can be placed into two informal groups, based on inflorescence position ( Stone 1989; Julius and Utteridge 2021). The first group has inflorescences strictly terminal on specialised lateral leafy branches, while the second group has inflorescences lateral (axillary) and/or terminal on the main stem and/or lateral branches. Ardisia recurvipetala falls into the second group, in which the majority of species in § Crispardisia belong, including six species from Peninsular Malaysia. Other than characters mentioned in the diagnosis, the new species can be easily recognised by its unbranched and subsessile inflorescences terminal on the main shoot and on relatively short specialised lateral branches with 1 to 2(-3) subtending leaves, tiny sepals (1.5-2 × 1-1.5 mm) that are yellowish-green and pinkish at base and corolla lobes that are strongly recurved at anthesis (Figs 1B , 3Bii).

Unlike other members of § Crispardisia , the leaf margins of the new species have both vascularised glands at the incisions between the crenatures and pustule-like structures along the crenations (Fig. 2 ); these result from the venation projecting from the leaf margin and should not be mistaken for bacterial nodules. This combination of vascularised glands and pustule-like structures is not observed in other Peninsular Malaysian members of § Crispardisia .

The new species is similar to Ardisia sphenobasis in having 17.5-23 cm long leaves (excluding reduced leaves subtending inflorescences on specialised lateral branches), but it has inflorescences that are terminal on the main shoot and specialised lateral branches (vs. strictly lateral on main stem). The whitish corollas of the new species are somewhat similar to those of A. villosa and A. crenata . However, A. recurvipetala (Fig. 3 ) differs in its largely glabrous flowers, except for short, simple eglandular and glandular hairs on the pedicels and calyx (vs. hairy throughout with long, villous hairs in A. villosa ). Compared to A. crenata , a widespread species with a whitish to pinkish corolla, branched and unbranched inflorescences and a flat and coriaceous lamina, the new species has corolla lobes with a creamy-white apex and a pink patch at the base, strictly unbranched inflorescences and chartaceous leaves with the lamina raised between the venation.

This latest addition brings the number of § Crispardisia species native to Peninsular Malaysia to ten. Of these, four species, including the new one, are endemic to Peninsular Malaysia: A. lankawiensis King & Gamble, A. minor King & Gamble, A. recurvipetala and A. recurvisepala Julius & Utteridge.

We consider species of Ardisia as important indicators of tropical and subtropical forest quality. Whilst some species are found in a range of habitats (e.g. A. elliptica Thunb.), many species have restricted distributions and habitat requirements, including several species of § Crispardisia . For example, in Peninsular Malaysia, A. lankawiensis is restricted to limestone habitats on Langkawi Islands and, in Thailand, A. pilosa H.R.Fletcher is restricted to the subtropical forests found on only Phu Kradeung mountain in north-east Thailand. That this new taxon is currently only found in unlogged areas within the Taman Negeri Kenyir suggests that A. recurvipetala is a useful indicator of primary forest within the forest reserve boundary. The discovery and description of new species is important. It contributes to naming and documenting our local biodiversity as part of a revision of the Primulaceae for the FPM, provides a better understanding of botanical distribution patterns and results in information about forest quality in Peninsular Malaysia.

Figures

Figure 1. Ardisia recurvipetala A habitat (inset: Ai habit Aii inflorescence position on lateral shoot and main stem) B lateral branch with flowers and young fruits C, D flowers.

Figure 2. Leaf margin showing vascularised glands (yellow arrow) on the incision between crenation and the pustule-like structures (red arrow) along the crenation.

Figure 3. Ardisia recurvipetala A flowering branches B flower bud (i), mature flower (ii) and flower with corolla removed (iii) C flower (spread) showing the stamen arrangement D adaxial view of sepal E ventral (left) and dorsal surfaces (right) of anther F anterior (left) and lateral views (right) of ovary G leaf margin with venation details and bacterial nodule H pustule-like structure on leaf margin crenation. Illustration by Mohd Aidil Nordin.

Figure 4. Map showing the type locality of Ardisia recurvipetala in Peninsular Malaysia.